maRci002

> Currently, a user has to explicitly use AndroidBackGesturePageTransitionsBuilder in order to get the predictive back transition, right? I wonder if it should be built into any of the existing...

> I'll try to make sure that we can do this kind of transition as well as the kind with the `animations` package. In that case, you would want to...

> @maRci002 Are you still available to work on this PR? I'm happy to take over work on this project myself if you're busy. Yes, this week I am going...

@justinmc, I am ready for a third review. I have found more documentation about predictive back [here](https://github.com/material-components/material-components-android/blob/master/docs/foundations/PredictiveBack.md).

> ### Back button doesn't work > If I try your example code at the top of this PR, just tapping the back button doesn't work. Sometimes nothing happens at...

> Let me know if you need help with the tests or reproducing the back button bug. Thank you for offering to help, I'd really appreciate it. I've been unable...

> I've pushed commits to fix the bug. The problem was for taps on the back button that Android was picking up as a back drag. We don't have a...

One problem that needs to be addressed before landing is the issue with nested `Navigator`s. The issue stems from the fact that typically, only the first `Navigator` participates in predictive...

> #### WidgetsBindingObserver.handleStartBackGesture /update/commit/cancel > Receives messages from the engine and allows listening. I debated pulling this out of WidgetsBinding into its own new class, but I think it makes...

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